In Brief:
Four-year outcomes for the Spine Patient Outcomes Research Trial spinal stenosis surgical and nonoperative cohorts are reported. Overall, 419 patients received surgery at some point during the first 4 years; 235 remained nonoperative. The proportion of enrollees who supplied data at each follow-up visit interval ranged from 67% to 89% with losses due to dropouts, missed visits, or deaths. The as-treated analysis combining the randomized and observational cohorts and adjusting for potential confounders found that the clinically significant advantages for surgery previously reported were maintained through 4 years.
